Gale Watch 8, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
211 AM EDT Sun Apr 12 2020

.SYNOPSIS...
High pressure will prevail through tonight. A warm front will
lift north Sunday, then a cold front will move through Monday.
High pressure will briefly rebuild early next week before a
coastal low pressure system moves through mid week. High
pressure will return Thursday and Friday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Early this morning: Overall, no concerns through sunrise. So
far, high clouds have been scattered at best and primarily
limited to the Georgia coast. The lack of cloud cover has
allowed temperatures to fall more than previously expected. Some
of this is being overcome by the warm onshore low level flow.
Made some adjustments to hourly temperature trends and sky
cover. The forecast remains dry through day break.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/...
Sunday: Warm frontogenesis will be ongoing along the Gulf coast
at daybreak Sunday as low pressure organizes across the
Southern Plains. The warm front will slowly sharpen through the
day as it propagates from south to north across the forecast
area. Guidance has been pretty consistent in showing an enhanced
corridor of isentropic assent/warm air advection generating a
fairly broad band of showers with a few tstms by mid-morning as
the warm front crosses the Altamaha River. This activity is
expected to traverse a good portion of the area through the day
with the greatest coverage occurring along/north of the I-16
corridor into southern South Carolina. 50-70% pops will be
highlighted with the highest pops north of I-16. Both surface
and mid-level instability values do not look overly strong, but
are certainly sufficient enough to support isolated to scattered
tstms. It would not be a complete surprise to see a strong tstm
or two develop in the vicinity of the warm front late morning
into the afternoon along the Savannah River north into southern
South Carolina as low-level wind fields strengthen, but
instability does not look sufficient enough to support anything
organized. Highs will range from the mid 70s across southern
South Carolina where rain and considerable cloud cover will
limit heating somewhat to the upper 70s/near 80 closer to the
Altamaha River. Breezy to locally windy conditions are expected
as mixing heights increase and begin to tap into strengthening
low-level wind fields. Cloud cover and precipitation should
limit mixing intensity somewhat, but winds 15-20 mph with gusts
25-30 mph still look possible, maybe a tad bit higher closer to
the coast and beaches.

Sunday Night into Monday: The warm front will be displaced well
to the north by sunset leaving all of Southeast South Carolina
and Southeast Georgia in the pre-frontal warm sector. The night
will be characterized as unseasonably warm and humid with
strengthening low- level jetting keeping the boundary layer
pretty well mixed. Lows are only expected to drop into the upper
60s-lower 70s as dewpoints rise to similar levels. There could
be a few coastal showers that make a run for the southern South
Carolina coast by late evening, but most areas should remain
rain-free once lingering afternoon convection wanes shortly
after sunset. Breezy to windy conditions likely and a Wind
Advisory could be needed for some areas, especially along the
lower South Carolina coast into the Charleston Tri-County area.

A large severe weather outbreak will be ongoing across portions
of the Deep South by early evening as squall line steadily
matures and marches east. The squall line is expected to reach
the far western zones by daybreak Monday, then move steadily
east to the coast through the morning hours. There is still
considerably uncertainty on how quickly the squall line will
move east with the various synoptic and mesoscale guidance
members showing differences by about 3 hours. If the line is
ends up moving slower than expected the overall severe risk will
increase as this will give the atmosphere a few additional
hours to destabilize even more. Even if this does not occur, the
combination of sufficient instability and impressive kinematic
profiles will support a risk for severe tstms embedded within
the squall line/LEWP with damaging winds being the primary
hazard. A risk for widespread damaging winds could evolve with
time if a well developed cold pool forms. 0-1km helicity is
forecast to strengthen to 350-500 m2/m2 by daybreak with SigTor
values of 2-4 units, highest across the Charleston Tri-County
area. These values could support a few tornadoes with a strong
tornado certainly possible given the sharp cyclonic kinking
patterns noted in model hodographs. There will be risk for
marginally severe hail in addition to damaging winds and
tornadoes. Pops 90-100% look reasonable for all areas Monday
morning with rain chances ending quickly with the passage of the
squall line. Highs will warm into the lower-mid 80s with
clearing expected as showers/tstms move offshore.

Monday night into Tuesday: The cold front does not look to push
offshore until Monday night then will return back to the north
Tuesday as weak low pressure develops over southern Georgia. The
front will be close enough to support isolated to scattered
showers and even a tstm or two across the central and southern
zones. Lows will range from the lower-mid 60s Monday night with
highs in the upper 70s to lower 80s Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
An approaching upper trough is expected to spur a coastal low
pressure system to develop and move northeast Tuesday night and
Wednesday. Numerous showers will affect the area as it lifts
northeast, then drier high pressure will build from the west.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
VFR conditions are expected to prevail at KCHS and KSAV through
late morning. An area of showers, with some potential for
embedded thunderstorms, will then develop across southeast
Georgia in the late morning/early afternoon. This area of
showers will then lift across the rest of the forecast area
through the rest of the afternoon. At KSAV, the main period for
showers and possibly a thunderstorm is 16-20z. MVFR ceilings
will prevail for much of the time thereafter, with some
potential for IFR ceilings in the evening hours. Kept the
forecast MVFR for now. At KCHS, showers and possibly a
thunderstorm will arrive later and impact the terminal starting
at around 20z. Similarly, IFR ceilings will be possible in the
evening but kept the forecast MVFR. Both sites will see gusty
south-southeast winds today with frequent gusts to around 30
knots. Gusty winds will start by mid morning and continue
through the rest of the period.

Extended Aviation Outlook: Periodic flight restrictions into
midday Monday as numerous showers and tstms affect the area.
Strong winds anticipated Sunday into Monday. Flight restrictions
again possible Tuesday night and Wednesday with numerous
showers associated with a coastal low.

&&

.MARINE...
Tonight: Southeast to south winds will prevail as the local
waters remain on the backside of surface high pressure. Winds
and seas will slowly increase through the night as the pressure
gradient tightens with the approach of low pressure well to the
west, although conditions will remain below Small Craft Advisory
criteria.

Sunday: Winds will steadily increase the coastal waters as low-
level jetting intensifies. Small Craft Advisories have been
posted for all waters beginning by noon for southeast winds
15-20 kt with gusts to 25 kt. Seas will correspondingly build
reaching 4-6 ft nearshore waters with 6-8 ft offshore waters by
afternoon. Winds will further increase Sunday night as the
strongest low-level jetting reaches the waters. Winds 25-30 kt
with gusts to 35-40 kt are expected over all legs except
Charleston Harbor where slightly lower should be realized. Gale
Watches have been raised per coordination with ILM, JAX and OPC.
A Gale Watch may be needed in the Charleston Harbor if
confidence increases.

Monday: Gale conditions in the morning will improve through the
day as the strongest low-level jet axis shifts east. A squall
line will move the waters during the morning and possibly early
afternoon brining a risk for wind gusts in excess of 50, hail
and possibly a waterspout or two.

Tuesday through Thursday: A brief Small Craft Advisory is
possible on Wednesday for the offshore GA waters due to 6 ft
seas building in a northeast flow as low pressure exits the
area.

Rip Currents: Increasing winds and waves in the surf zone will
support a moderate risk at all beaches Sunday. The risk remains
moderate for the GA coast Monday but increases to the high
category for the SC beaches Monday (especially in the morning)
as winds and waves peak with breakers of 4-7 ft ahead of a line
of thunderstorms.

&&

.TIDES/COASTAL FLOODING...
Higher than normal tides are expected the next several days due
to astronomical influences from the full moon and perigee.
Additionally, winds are forecast to be onshore Sunday into
Monday morning, which could further elevate the tides. As a
result, minor coastal flooding is expected around the high tide
just after midnight early Monday morning.

High Surf: Strong southerly flow ahead of a cold front will
result in building nearshore seas Sunday afternoon into Sunday
night. With seas as high as 9-11 ft within 20 NM of shore,
breaker heights could exceed 5 ft at times Sunday night into
Monday morning, necessitating a High Surf Advisory. The risk for
5+ft breakers looks highest along the southern South Carolina
coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from noon today to 5 PM EDT Monday for
     AMZ330.
     Gale Watch from this evening through Monday morning for AMZ350-
     352-354.
     Small Craft Advisory from noon today to 9 PM EDT this evening
     for AMZ350-352-354.
     Gale Watch from this evening through Monday morning for AMZ374.
     Small Craft Advisory from noon today to 6 PM EDT this evening
     for AMZ374.

&&

NEAR TERM...BSH
SHORT TERM...ST
LONG TERM...JRL
AVIATION...BSH/ST
MARINE...RJB/ST
TIDES/COASTAL FLOODING...

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE CHARLESTON SC
1258 AM EDT SUN APR 12 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1218 AM     HIGH ASTR TIDES  1 E CHARLESTON          32.78N  79.93W
04/12/2020                   CHARLESTON         SC   TIDE GAGE

            A MAXIMUM TIDE LEVEL OF 7.09 FT MLLW (1.33 FT MHHW) WAS
            OBSERVED AT THE CHARLESTON HARBOR TIDE GAGE. SHALLOW
            COASTAL FLOODING TYPICALLY BEGINS ALONG THE LOWER SOUTH
            CAROLINA COAST WHEN TIDE LEVELS REACH 7.0 FT MLLW (1.24
            FT MHHW) IN THE CHARLESTON HARBOR.

&&

EVENT NUMBER CHS2000129

BSH